Despite the huge similarity between Nakiri and Usuba. These blades have the same use, of course, but with very different characteristics.
Both blades are designed for cutting vegetables.
The Usuba is a traditional Japanese blade, as such it features an asymmetrical geometry with a unique bevel. Its use will therefore be reserved for either left-handed or right-handed people, moreover a single bevel blade requires more expertise for its use.
The Nakiri actually derives from a Usuba but with a symmetrical blade and therefore with a double bevel for ambidextrous use. This blade was born due to its great popularity in the West, where we are not necessarily used to using asymmetrical blades.
Generally a usuba blade has a thicker “back” than a nakiri, only to taper off drastically on the bevel until reaching an extremely fine edge.
So a nakiri blade has a fairly generalized smoothness over the entire blade.